Apparatus for and method of withdrawing ions in EUV light production apparatus

ABSTRACT

An ion withdrawal apparatus that withdraws ions emitted from a plasma in an EUV light production apparatus in which a target at an EUV light production point is irradiated with laser light to be made in a plasma state and the target emits EUV light, the ion withdrawal apparatus which includes: a collector mirror that is disposed in a direction opposite to a laser light incidence direction to collect the EUV light and has a hole for the ions to pass therethrough; magnetic line of force production means that produces a magnetic line of force that is parallel or approximately parallel to the laser light incidence direction at or in the vicinity of the EUV light production point; and ion withdrawal means that is disposed on the opposite side of the collector mirror from the EUV light production point and withdraws the ions.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/406,388, filed Mar. 18, 2009, which application claims priority ofJapanese Application No. 2008-106907, filed Apr. 16, 2008, the entirecontents of which are incorporate herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an EUV light production apparatus thatis used as a light source for an exposure system and so on, andparticularly, to an apparatus for and a method of withdrawing ionsemitted from a target that has been made in a plasma state at an EUVlight production point.

2. Description of Related Art

A light lithography technique, in which a circuit pattern is opticallytransferred on a semiconductor wafer, is important for realizing theintegration in an LSI. As an exposure system used for light lithography,one that employs a reduced projection exposure method, i.e. a stepper,is utilized at present. Specifically, a light transmitted through anoriginal image (reticule) pattern irradiated with a light source isprojected on a light-sensitive material on a semiconductor substrate viaa reduced projection optical system to form a circuit pattern. Theresolution of the projected image is limited in accordance with thewavelength of the light source. For this reason, with a demand formaking the width of lines of a pattern finer, the wavelength of thelight source is getting shorter toward an ultraviolet region.

Recently, KrF excimer laser (wavelength: 248 nm) and ArF excimer laser(wavelength: 193 nm), which oscillate to produce deep ultraviolet light(DUV light), are used as a light source, and F2 laser, which oscillatesto produce vacuum ultraviolet light (VUV light), is developed.

At present, in order to realize a finer process, attempts are made touse an extreme ultraviolet (EUV) light source (wavelength: 13.5 nm),which outputs EUV light, as a light source for light lithography.

There is a laser production plasma (LPP) method as one of methods forproducing the EUV light.

With an EUV light source employing the LPP method, a target isirradiated with short-pulse laser light so that the target is excitedinto a plasma state in which the EUV light is produced, and then theproduced EUV light is collected by a collector mirror to be output.

FIG. 1 is a view conceptually showing a configuration of an EUV lightproduction apparatus employing the LPP method and used as a light sourcefor an exposure system.

A collector mirror 3 for collecting EUV light is provided inside avacuum chamber 2. The EUV light collected by the collector mirror 3 istransmitted to an exposure system (not shown) provided outside thevacuum chamber 2. The exposure system is a system for formingsemiconductor circuit patterns on a semiconductor wafer with the EUVlight.

A vacuum is drawn on the inside of the vacuum chamber 2 by means of avacuum pump or the like to evacuate the inside because the EUV lighthaving a short wavelength of 13.5 nm is not effectively transmitted ifnot under vacuum.

A target 1 serving as a EUV light production source is located on apredetermined EUV light production point A in the vacuum chamber 2,namely, a condensing point of laser light. Tin Sn, lithium Li, xenon Xe,or the like is used as a material for the target 1.

A driver laser unit 4 serving as a laser oscillator performspulse-oscillation to produce and emit laser light L. Nd:YAG laser, CO₂laser, or the like is used as a laser.

The laser light L via a laser condenser system is condensed on the EUVlight production point A. The target 1 is irradiated with the laserlight L at the timing when the target 1 reaches the EUV light productionpoint A. The irradiation of the laser light L onto the target 1 makesthe target 1 excited into a plasma state so that the target 1 emits EUVlight.

The emitted EUV light diverges in all the directions centered on theplasma. The collector mirror 3 is disposed so as to surround the plasma.The EUV light that diverges in all the directions is collected by andreflected on the collector mirror 3. The collector mirror 3 selectivelyreflects the EUV light having a desired wavelength of 13.5 nm. The EUVlight (output EUV light) reflected on the collector mirror 3 istransmitted to an exposure system.

The plasma emits neutral particles and ions having various velocities.

Meanwhile, with the demand for higher EUV light output, it is requiredto employ a high output laser unit as the driver laser unit 4 while highand stable output of the EUV light is maintained for a long period oftime.

The neutral particles and ions emitted from the plasma are, however,deleterious in terms of the durability of the EUV light productionsystem and the efficiency of the light output.

Specifically, since the collector mirror 3 is disposed in the vicinityof the plasma, the neutral particles and low-speed ions emitted from theplasma adhere to a reflection plane of the collector mirror 3, causing adeterioration in the index of reflection of the collector mirror 3.

On the other hand, high-speed ions emitted from the plasma damagemultilayered film formed on the reflection plane of the collector mirror3. This is called “spattering.”

The production of the neutral particles can be suppressed by using atarget having a minimum mass as disclosed in International PublicationNo. WO 2002/46839 pamphlet, page 1, or by producing a completely ionizedplasma by means of double pulse irradiation or the like.

The production of ions, however, is inevitable so long as the plasma isproduced so that measures against the ions are indispensable.

As described above, low-speed ions adhere to the collector mirror 3, anddeteriorate the index of reflection of the collector mirror 3. The ionsthat have adhered to the collector mirror 3, however; can be removed inprinciple by cleaning with reacted gas or the like as disclosed in U.S.2006/0091109A1. After the cleaning, the index of reflection of thecollector mirror 3 recovers, and hence the collector mirror 3 may becontinuously used.

However, for the EUV light production apparatus used for exposure,recently there has been a demand to prolong, up to at least one year,the period when the 10% deterioration occurs in the index of reflectionof the collector mirror 3. To meet the demand, the allowed value of theadhesion amount (thickness) of a metallic film on the reflection planeof the collector mirror 3 is very small value, e.g. about 0.75 nm if thetarget 1 is made of tin Sn. The high rate and high speed of cleaning aretherefore required.

On the other hand, the high-speed ions spatter the surface of thecollector mirror 3 as described above to damage the reflection film ofthe collector mirror 3, resulting in a deterioration in the index ofreflection of the collector mirror 3. Replacement of the collectormirror 3 is required when the collector mirror 3 is damaged and theindex of reflection thereof deteriorates. There is a technique ofreproducing the reflection film of the collector mirror 3 of the EUVlight production apparatus. In such a technique, however, a coating unitfor precisely carrying out a coating process with good evenness ofsurface, e.g. about 0.2 nm (rms) is additionally provided, which leadsto the increase in the cost of the apparatus. Also, since the damage inthe reflection film of the collector mirror 3 varies from place toplace, it is substantially impossible to reproduce the reflection filmhaving even dispersion of the index of reflection. For this reason, itis general to laminate reflection films having hundreds of layers on thecollector mirror 3 in order to increase the lifetime until thereplacement of the collector mirror 3.

Further, as a method for reducing the damage density due to thehigh-speed ions, the distance between the collector mirror 3 and the EUVlight generation point A may be set longer. According to this method,however, the collection solid angle of the collector mirror 3 forcollecting the EUV light becomes small, which may cause a problem thateffective EUV output for exposure becomes low.

In order to solve the above problem, the collector mirror 3 having alarge diameter, e.g. 500 mm or more may be used. However, if thecollector mirror 3 having such a large diameter is manufactured, it isdifficult to produce the reflection films having hundreds of layerswhite keeping the accurate surface roughness and geometry. Further, evenif the collector mirror 3 as described above could be manufactured, themanufacturing process would become complicated and the time required forit would become long, resulting in the collector mirror 3 being veryexpensive.

Meanwhile, the radiation intensity distribution of the EUV light isdependent upon a laser light incidence direction. Specifically, therelatively strong EUV light is emitted in the direction opposite to thelaser light incidence direction. There is therefore proposed a systemconfiguration in which the collector mirror 3 is provided with a holefor the laser light to pass therethrough, and the laser light is emittedtoward the target 1 via the hole, whereby the strong EUV light iseffectively collected by the collector mirror 3 disposed at a placewhere the collector mirror 3 faces a direction opposite to the laserlight incidence direction. It should be noted that the term “laser lightincidence direction” herein is used to mean the direction of the laserlight when the laser light is emitted onto the EUV light productionpoint A.

Furthermore, it was recently found out that not only the above mentionedradiation intensity distribution of the EUV light but also the quantityand intensity (kinetic energy) distribution of the ions emitted from theplasma are dependent upon the laser light incidence direction. That is,as shown in FIG. 2, the quantity and intensity (kinetic energy) of ionsemitted are large and strong (high) in the direction opposite to thelaser light incidence direction. Accordingly, if the collector mirror 3is disposed at a place where the collector mirror 3 faces the directionopposite to the laser light incidence direction as shown by an alternatelong and short dash line in FIG. 2, a problem may occur that thecollector mirror 3 is vigorously damaged and the lifetime thereofbecomes extremely short.

In order to solve the above problem, as shown in FIG. 3, Japanese PatentApplication Laid-open No. 2005-197456 discloses that, by applying amagnetic field to the ions emitted from the plasma by means of magnetssuch that magnetic lines of force are in the direction perpendicular tothe laser light incidence direction, the ions emitted from the plasmaare deflected to the above perpendicular direction not to reach thecollector mirror 3, thereby preventing the ion adhesion and thespattering on the collector mirror 3.

As to the invention disclosed in the Japanese Patent ApplicationLaid-open No. 2005-197456, however; several Ts of strong magnetic fieldare required to deflect the high-speed ions reaching 10 keV in order toprevent them from reaching the collector mirror 3, and accordingly thecost of the electromagnet for applying the magnetic field becomes high.As a result the total cost of the EUV light production apparatus becomeshigh.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems, andan object of the present invention is to remarkably suppressunrecoverable damages of the collector mirror 3 caused by the high-speedions, and the adhesion, which is allowed only a little, of low-speedions to the collector mirror 3 while reducing the cost required for theEUV light production apparatus, and also to effectively carry out thecollection of the EUV light by the collector mirror 3.

In order to accomplish the object, a first aspect of the presentinvention provides an ion withdrawal apparatus that withdraws ionsemitted from a plasma in an EUV light production apparatus in which atarget at an EUV light production point is irradiated with laser lightto make a plasma state and the target emits EUV light, the ionwithdrawal apparatus which includes: a collector mirror that is disposedin a direction opposite to a laser light incidence direction to collectthe EUV light and has a first hole for the ions to pass therethrough;first magnetic line of force production means that produces a magneticline of force that is parallel or approximately parallel to the laserlight incidence direction at or in the vicinity of the EUV lightproduction point; and ion withdrawal means that is disposed on theopposite side of the collector mirror from the EUV light productionpoint and withdraws the ions.

According to a second aspect of the present invention, the collectormirror has a hole for the laser light to pass therethrough and reach theEUV light production point.

According to a third aspect of the present invention, the ion withdrawalapparatus according to the first or second aspect of the presentinvention further includes magnetic line of force production means thatfurther converges the magnetic line of force at an entrance of the ionwithdrawal means to make the flux density higher.

According to a fourth aspect of the present invention, the ionwithdrawal apparatus according to the first or second aspect of thepresent invention further includes voltage application means thatapplies a voltage on the ions to correct orbits of the ions at anentrance of the ion withdrawal means to introduce the ions into theentrance.

According to a fifth aspect of the present invention, the ion withdrawalapparatus according to the first or second aspect of the presentinvention further includes magnetic line of force production means thatproduces the magnetic line of force so as to deflect the ions toward anentrance of the ion withdrawal means.

According to a sixth aspect of the present invention) the ion withdrawalapparatus according to the first or second aspect of the presentinvention further includes voltage application means that applies avoltage on the ions so as to deflect the ions toward an entrance of theion withdrawal means.

According to a seventh aspect of the present invention, the magneticline of force is deflected toward an entrance of the ion withdrawalmeans by disposing the magnetic line of force so as to be inclined withrespect to the collector mirror in the ion withdrawal apparatusaccording to the first or second aspect of the present invention.

According to an eighth aspect of the present invention, the ionwithdrawal apparatus according to the sixth aspect of the presentinvention further includes a laser condenser system that condenses thelaser light, a voltage being applied on the system.

According to a ninth aspect of the present invention, the lasercondenser system and the magnetic line of force production means aredisposed such that an incident axis of the laser light and a centralaxis of a magnetic field coincide or approximately coincide in the ionwithdrawal apparatus according to the eighth aspect of the presentinvention.

According to a tenth aspect of the present invention, the target is arotating disk target, a grooved wire target, or a hollowed wire targetin the ion withdrawal apparatus according to the first or second aspectof the present invention.

An eleventh aspect of the present invention provides a method ofwithdrawing ions emitted from a plasma in an EUV light productionapparatus in which a target at an EUV light production point isirradiated with laser light to be made in a plasma state and the targetemits EUV light, the method which includes: producing a magnetic line offorce that is parallel or approximately parallel to the laser lightincidence direction at or in the vicinity of the EUV light productionpoint; allowing the magnetic line of force to trap the ions; moving thetrapped ions along the magnetic line of force; and introducing thetrapped ions via a hole provided to a collector mirror into an entranceof ion withdrawal means to withdraw the trapped ions.

In the first aspect of the present invention, as shown in FIG. 4, acollector mirror 3 is disposed in a direction opposite to a laser lightincidence direction, and collects EUV light. The collector mirror 3 hasa hole 3 e for the ions to pass therethrough.

Magnetic line of force production means 40 produces a magnetic line offorce that is parallel or approximately parallel to the laser lightincidence direction at or in the vicinity of the EUV light productionpoint A (FIG. 5).

Ion withdrawal means 30 is disposed on the opposite side of thecollector mirror 3 from the EUV light production point A. The ionwithdrawal means 3 withdraws the ions.

In the first aspect, as shown in FIG, 5, a magnetic line of force thatis parallel or approximately parallel to the laser light incidencedirection at or in the vicinity of the EUV light production point A isproduced. Accordingly, the magnetic line of force is allowed to trap theions. The trapped ions move along the magnetic line of force. Thetrapped ions are then introduced into an entrance 30A of ion withdrawalmeans 30 via a hole 3 e provided to the collector mirror 3. As a result,the trapped ions are withdrawn.

With the first aspect of the present invention, the magnetic line offorce production means (magnet 40) can be made small and the costrequired for the EUV light production apparatus can be reduced. Further,unrecoverable damages of the collector mirror 3 caused by the high-speedions, and the adhesion, which is allowed only a little, of low-speedions to the collector mirror 3 are remarkably suppressed. Furthermore,the collection of the EUV light by the collector mirror 3 can beeffectively carried out.

In the second aspect of the present invention, the collector mirror 3has a laser passage hole 3 d for the laser light L to pass therethroughas shown in FIGS. 4B and 4C. The laser light L passes through the laserpassage hole 3 d of the collector mirror 3 to reach the EUV lightproduction point A.

In the third aspect of the present invention, as shown in FIG. 7, thereis additionally provided magnetic line of force production means(supplementary magnet 45 or supplementary core 46) for furtherconverging the magnetic line of force at the entrance 30A of the ionwithdrawal means 30 to make the flux density higher.

In the fourth aspect of the present invention, as shown in FIG. 9, thereis additionally provided voltage application means 50 (direct current orpulse power supply 51, electrode 52) for applying a voltage on the ionsto correct orbits of the ions at the entrance 30A of the ion withdrawalmeans 30 to be introduced thereinto.

In the fifth aspect of the present invention, as shown in FIG. 10, thereis additionally provided magnetic line of force production means(magnets 47, 49 for deflection, or core 48 for deflection) for producingthe magnetic line of force to deflect the ions toward the entrance 30Aof the ion withdrawal means 30.

In the sixth aspect of the present invention, as shown in FIG. 11, thereis additionally provided voltage application means 55 (direct current orpulse power supply 56, electrode 57) for applying a voltage on the ionsto deflect the ions toward the entrance 30A of the ion withdrawal means30.

In the seventh aspect of the present invention, as shown in FIG. 13, themagnetic line of force is deflected toward the entrance 30A of the ionwithdrawal means 30 by disposing the magnetic line of force productionmeans (magnet 40) so as to be inclined with respect to the collectormirror 3.

In the eighth aspect of the present invention, as shown in FIG. 14, avoltage is applied on a laser condenser system 8 (collector mirror 8A)for condensing the laser light. Accordingly, the laser condenser system8 (collector mirror 8A) functions as the electrode for deflection as isthe case with the sixth aspect of the present invention. As a result,the ions are deflected toward the entrance 30A of the ion withdrawalmeans 30.

In the ninth aspect of the present invention, as shown in FIGS. 10, 11,12, 13, and 14, the laser condenser system 8 and the magnetic line offorce production means (magnet 40) are disposed such that an incidentaxis of the laser light and a central axis of a magnetic field coincideor approximately coincide.

In the tenth aspect of the present invention, as shown in FIG. 15, thetarget 1 is formed by a rotating disk target 1B, a grooved wire target1C, or a hollowed wire target 1D.

The eleventh aspect of the present invention provides a methodcorresponding to the apparatus according to the first aspect of thepresent invention. Specifically, as shown in FIG. 5, the methodincludes 1) producing a magnetic line of force that is parallel orapproximately parallel to the laser light incidence direction at or inthe vicinity of the EUV light production point A; 2) allowing themagnetic line of force to trap the ions; 3) moving the trapped ionsalong the magnetic line of force; and 4) introducing the trapped ionsvia a hole 3 e provided to the collector mirror 3 into an entrance 30Aof ion withdrawal means 30 to withdraw the trapped ions.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a view for explaining a conventional art, conceptually showingthe configuration of an EUV light production apparatus that employs anLPP method;

FIG. 2 is a view for explaining that the quantity and intensity (kineticenergy) of emission of ions become large and strong (high) in thedirection opposite to a laser light incidence direction;

FIG. 3 a view for explaining another conventional art, specificallyshowing a configuration for applying a magnetic field to the ionsemitted from a plasma such that magnetic lines of force are formed inthe direction perpendicular to the laser light incidence direction;

FIGS. 4A through 4C are views showing a configuration of an apparatusaccording to a first embodiment. FIG. 4A shows the overall configurationof the apparatus, and FIGS. 4B and 4C show a reflection plane of acollector mirror;

FIG. 5 is a view for explaining the relation between magnetic lines offorce formed by magnets and behavior of ions emitted from the plasma;

FIGS. 6A and 6B are views for explaining the relation between themagnetic lines of force and kinetic energy of an ion. FIG. 6A is a viewfor explaining the first embodiment and FIG. 6B is a view for explainingthe conventional art shown in FIG. 3;

FIGS. 7A and 7B are views showing configurations of an apparatusaccording to a second embodiment;

FIGS. 8A and 8B are views showing configurations of an apparatusaccording to a third embodiment;

FIG. 9 is a view showing a configuration of an apparatus according to afourth embodiment;

FIGS. 10A through 10C are views showing configurations of an apparatusaccording to a fifth embodiment;

FIGS. 11A through 11C are views showing configurations of an apparatusaccording to a sixth embodiment;

FIG. 12 is a view showing a configuration of an apparatus according to aseventh embodiment;

FIG. 13 is a view showing a configuration of an apparatus according toan eighth embodiment;

FIG. 14 is a view showing a configurations of an apparatus according toa ninth embodiment; and

FIGS. 15A through 15C are views showing configurations of an apparatusaccording to a tenth embodiment, and particularly showing examples of atarget other than a droplet target.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of an apparatus for and a method of withdrawing ions in anEUV light production apparatus will be described with reference to theaccompanying drawings.

First Embodiment

FIGS. 4A through 4C are views showing a configuration of an apparatusaccording to a first embodiment. FIG. 4A shows the overall configurationof the apparatus, and FIGS. 4B and 4C show a reflection plane 3A of acollector mirror 3.

The EUV light production apparatus shown in FIG. 4A has a target 1located on EUV light production point A in a plasma state to allow it toproduce EUV light and output it outside, like the apparatus shown inFIG. 1.

The EUV light production apparatus employs an LLP method and is used asa light source for an exposure system (not shown).

Specifically, a collector mirror 3 for collecting EUV light is providedinside a vacuum chamber 2 (not shown) of the EUV light productionapparatus. The EUV light collected by the collector mirror 3 istransmitted to the exposure system provided outside the vacuum chamber2, like the apparatus shown in FIG. 1. The exposure system is a systemfor forming semiconductor circuit patterns on a semiconductor wafer withthe EUV light.

A vacuum is drawn on the inside of the vacuum chamber 2 by means of avacuum pump or the like to evacuate the inside, and gas in the vacuumchamber is exhausted to outside by an exhaust unit. The reason why aspace for producing the EUV light is evacuated is that the EUV lighthaving a short wavelength of 13.5 nm is not effectively transmitted ifnot under vacuum.

A target 1 serving as a EUV light production source is supplied to apredetermined EUV light production point A, namely a condensing point oflaser light L, in the vacuum chamber as a droplet 1A. A target injectionunit 6 injects the droplet 1A toward the EUV light production point A,in other words, drops the droplet immediately below.

The droplet 1A is a liquid metal, metallic solution, metallic compoundsolution, or colloid solution containing metallic particles or metalliccompound particles.

In a case where the target 1 in the droplet 1A is formed by a metal, amain constituent of the metal is tin Sn, lithium Li, or the like.

In a case where the target 1 in the droplet 1A is formed by a metalliccompound, a main constituent of the metallic compound is tin oxide SnO₂,or the like.

A main constituent of the solvent of the droplet 1A may be a liquidhaving dispersibility, an organic solvent, water, a liquid nitrogen, ora liquid xenon. The organic solvent may be methanol, ethanol, acetone,or mixture solution of them.

A description will be given hereinafter supposing that the droplet 1A iscolloid solution containing metallic particles of tin Sn or metalliccompound particles of tin oxide SnO₂.

A driver laser unit 4 serving as a laser oscillator performs pulseoscillation to produce and emit the laser light L. The laser used is aCO₂ laser. Note that other lasers such as Nd:YAG laser may be employed.

The laser light L is condensed on the EUV light production point A via alaser condenser system 8 comprising condenser lens and so on. The target1 is irradiated with the laser light L at the timing when the target 1in the droplet 1A reaches the EUV light production point A. Theirradiation of the laser light L on the target 1 makes the targetexcited into a plasma state to emit the EUV light. That is, the target1, which is a fixed space where the metallic particles, the metalliccompound particles, or an aggregate of metallic particles or metalliccompound particles disperses, is excited into the plasma state.

The emitted EUV light 5 diverges in all the directions centered on theplasma. It should be noted that, as described above, the radiationintensity distribution of the EUV light is dependent upon the laserlight incidence direction and thus the relatively strong EUV light isemitted in the direction opposite to the laser light incidencedirection.

The collector mirror 3 is disposed so as to surround the plasma. Thecollector mirror 3 is disposed in a direction opposite to the laserlight incidence direction. Thus, the collector mirror 3 effectivelycollects relatively strong EUV light emitted in the direction oppositeto the laser light incidence direction among the EUV light emitted inall the direction, and then reflects the collected EUV light. Thecollector mirror 3 selectively reflects the EUV light having a desiredwavelength of 13.5 nm. A coating, such as an Mo/Si film, having a highindex of reflection around the wavelength of 13.5 nm, is applied to thecollector mirror 3. The EUV light (output EUV light) reflected on thecollector mirror 3 is transmitted to an exposure system (not shown).

The plasma emits ions. As described above with reference to FIG. 2, thequantity and intensity (kinetic energy) distribution of the ions emittedfrom the plasma are dependent upon the laser light incidence direction.Particularly, the radiation amount and intensity (kinetic energy) of theions emitted in the direction opposite to the laser light incidencedirection is large and strong (high).

An ion withdrawal unit 30 is disposed on the opposite side of thecollector mirror 3 from the EUV light production point A. The ionwithdrawal unit 30 introduces the ions through an entrance 30A thereof.The ion withdrawal unit 30 comprises a filter; a vacuum pump, etc., andwithdraws the ions by trapping them, or drawing the vacuum to exhaustthem outside.

Characteristic elements of the apparatus according to the firstembodiment will be described hereinbelow.

The collector mirror 3 is disposed in the direction opposite to thelaser light incidence direction. The collector mirror 3 is also disposedsuch that reflection plane 3A thereof faces the EUV light productionpoint A while a central axis 3 c thereof is perpendicular to theinjection direction (direction immediately below in FIG. 4A) of thedroplet 1A from the target injection unit 6. Hereinunder, arrangement ofthe elements of the apparatus will be described suitably on the basis of“the central axis 3 c of the collector mirror 3.”

The collector mirror 3 has a laser passage hole 3 d through which thelaser light L passes as shown in FIGS. 4B and 4C. The driver laser unit4 and laser condenser system 8 are arranged such that the laser light Lpasses through the laser passage hole 3 d. The laser light L advancesupwardly in the figures at a predetermined angel with respect to thecentral axis 3 c of the corrector mirror 3 and then reaches the EUVlight production point A.

The collector mirror 3 also has an ion collection hole 3 e through whichthe ions passed as shown in FIGS. 4B and 4C. The ion collection hole 3 eis formed in a higher position than the laser passage hole 3 d. The ioncollection hole 3 e is formed such that the center thereof coincideswith the central axis 3 c of the collector mirror 3.

The ion collection hole 3 e may be formed apart from the laser passagehole 3 d as shown in FIG. 4B. Alternatively, the ion collection hole 3 emay be formed such that the ion collection hole 3 e and the laserpassage hole 3 d are linked together to form a rectangular-shaped holeas a whole.

In this embodiment, a description is given on the assumption that thecollector mirror 3 has the laser passage hole 3 d and the laser L passesthrough the collector mirror 3 to reach the EUV light production pointA. However, as will be described later, depending on the arrangement ofthe driver laser unit 4 and laser condenser system 8, it is notnecessary for the laser light L to pass through the collector mirror 3so long as the laser light incidence direction is parallel orapproximately parallel to the magnetic lines of force at or in thevicinity of the EUV light production point A.

The ion withdrawal unit 30 is disposed in the direction perpendicular tothe injection direction of the droplet 1A from the target injection unit6, in other words, disposed in the direction of the central axis 3 c ofthe collector mirror 3.

A magnet 40 as magnetic line of force production means is arrangedaround the periphery of the collector mirror 3.

The magnet 40 produces magnetic lines of force parallel or approximatelyparallel to the magnetic lines of force at or in the vicinity of the EUVlight production point A.

FIG. 5 is a view for explaining the relation between the magnetic linesof force formed by the magnet 40 and the behavior of the ions emittedfrom the plasma.

Hereinbelow, the operation and effect of the elements of the apparatusaccording to the first embodiment will be described.

With the apparatus of the first embodiment, the target injection unit 6injects the droplet 1A toward the EUV light production point A, in otherwords, drops it.

On the other hands, the driver laser unit 4 emits the laser light L. Theemitted laser light L advances via the laser condenser system 8 towardthe collector mirror 3, passes through the laser passage hole 3 d, andthen reaches the EUV light production point A. The target 1 isirradiated with the laser light L at the timing when the target 1reaches the EUV light production point A. The irradiation of the laserlight L on the target 1 makes the target excited into a plasma state sothat the target 1 emits the EUV light.

Relatively strong EUV light is emitted in the direction opposite to thelaser light incidence direction. Thus, the EUV light is effectivelycollected by the collector mirror 3 disposed in the direction oppositeto the laser light incidence direction. The collector mirror 3 reflectsthe collected EUV light. The EUV light (output EUV light) reflected onthe collector mirror 3 is transmitted to an exposure system (not shown).

The plasma emits ions. As described above with reference to FIG. 2, thequantity and intensity (kinetic energy) distribution of the ions emittedfrom the plasma are also dependent upon the laser light incidencedirection. Particularly, the radiation amount and intensity (kineticenergy) of the ions emitted in the direction opposite to the laser lightincidence direction is large and strong (high).

The ions move in a magnetic field produced by the magnet 40. As wellknown, Lorentz force acts on an ion, which is a charged particle, in amagnetic field and thus the ion advances along a magnetic line of forcewhile rotating around the magnetic line of force with a certain Larmorradius. That is, the ion is trapped in the magnetic line of force andthen moves along the magnetic line of force.

The magnet 40 produces magnetic lines of force parallel or approximatelyparallel to the magnetic lines of force at or in the vicinity of the EUVlight production point A. Accordingly, the direction of the magneticlines of force approximately coincides with an initial movementdirection of the ion. Specifically, as shown in FIG. 5, as for theinitial movement direction, almost all the ions are emitted from theplasma in a state where the component parallel to the magnetic line offorce accounts for a large part, while the component perpendicular tothe magnetic line of force accounts for a small part. Larmor radiustherefore becomes short and thus high-speed ions converge on a narrowrange. Since the convergence range of the high-speed ions is narrow, thehigh-speed ions surely pass through the ion collection hole 3 e of thecollector mirror 3. As a result, the ion collection hole 3 e may be madenarrow. After passing through the ion collection hole 3 e of thecollector mirror 3, the high-speed ions further advance along themagnetic lines of force and then are introduced into the entrance 30A ofthe ion withdrawal unit 30 to be withdrawn. Since the convergence rangeof the high-speed ions is narrow, the structure of the ion withdrawalunit 30 may be simplified such that the entrance 30A thereof may be madenarrow. For example, when an Sn droplet having several tens μm ofdiameter is irradiated with a CO₂ laser having intensity up to 109 W/cm²and the high-speed ions are collected on the central magnetic field upto 2 T, the high-speed ions can be converged on a range of ten andseveral mm of diameter at a place 100 mm apart from the plasmaproduction point A. Consequently, the diameters of the ion collectionhole 3 e of the collector mirror 3 and the entrance 30A of the ionwithdrawal unit 30 may be set in accordance with this convergence rangeof ten and several mm of the high-speed ions.

As described above, according to this embodiment, it is possible toeffectively converge the high-speed ions that may cause the damage ofthe collector mirror 3 and to withdraw them without any collisionagainst the collector mirror 3 while maintaining high efficiency of EUVlight collection. This is apparent if compared with the case in which amagnetic field is not applied by the magnet 40. More specifically, ifthe magnetic field is not applied, the high-speed ions emitted from thetarget 1, in general, are produced mainly in the direction opposite tothe laser light incidence direction, but diffuses in all the directionas time passes as shown in FIG. 2. Accordingly, the highspeed ions areemitted on the whole reflection plane 3A, which extremely shortens thelifetime of the collector mirror 3. In contrast, as shown in FIG. 5,according to this embodiment, since the magnet 40 produces a magneticfield at or in the vicinity of the EUV light production point A todefine magnetic lines of force parallel or approximately parallel to thelaser light incidence direction, the diffusing high-speed ions can bedeflected to converge on a narrow range. For this reason, it is possibleto converge the high-speed ions on a narrow range on the reflectionplane 3A of the collector mirror 3, namely a range corresponding to theion collection hole 3 e, and allow the high-speed ions to pass throughthe collector mirror 3 without colliding with collector mirror 3 so asto be withdrawn.

According to this embodiment, almost all the high-speed ions emittedfrom the plasma can be withdrawn. However, the periphery of the ioncollection hole 3 e may be liable to suffer the collision of the ionsdue to minor ions at an edge of the kinetic energy distribution at thetime of production of the ions and various instabilities though thisprobability is low. In this view, the periphery of the ion collectionhole 3 e of the collector mirror 3 may be formed by the partiallyreplaceable mirror 3B, which is partially replaceable, as shown in FIG.4C. Accordingly, only the partially replaceable mirror 3B can bereplaced when the partially replaceable mirror 3B has almost run downbefore other parts of the collector mirror 3. Consequently, maintenancecost thereof can be further reduced as compared with a case in which thewhole collector mirror 3 is replaced.

Furthermore, according to this embodiment, the magnet 40 may beintroduced at low cost so that the whole cost of the EUV rightproduction apparatus can be reduced. This is apparent if compared withthe conventional art as described above with reference to FIG. 3.

FIG. 3 shows an apparatus in which the magnets 140, 140 are respectivelydisposed above and below the collector mirror 3 to form a mirrormagnetic field so that the high-speed ions are discharged in upward anddownward directions of the mirror magnetic field.

Unlike the apparatus according to this embodiment, the magnetic lines offorce in the apparatus shown in FIG. 3 are produced perpendicular to thelaser light incidence direction.

FIGS. 6A and 6B are views for explaining the relation between themagnetic lines of force and the kinetic energy of an ion.

FIG. 6A is a view for explaining the first embodiment, in which themovement direction of the ions is approximately parallel to the magneticlines of force, and FIG. 6B is a view for explaining the conventionalart shown in FIG. 3, in which the movement direction of the ions isapproximately perpendicular to the magnetic lines of force.

Supposing, for example, that conditions of the target 1 and laseremission of the apparatus according to the first embodiment areequivalent to those of the prior apparatus shown in FIG. 3, the kineticenergies E of the high-speed ions in FIG. 6A and FIG. 6B becomeequivalent to each other. Here, among the kinetic energy E of thehigh-speed ion, the component parallel to the laser light incidencedirection is denoted as Ex and the component perpendicular to the laserlight incidence direction is denoted as Ez.

The direction B in the magnetic lines of force is approximately parallelto the kinetic energy E of the ions in this embodiment (FIG. 6A) whilethe direction B in the magnetic lines of force is approximatelyperpendicular to the kinetic energy E of the ions in the conventionalart (FIG. 6B). Therefore, in the apparatus of the first embodiment,among the kinetic vectors of the high-speed ions, a direction in whichthe high-speed ions are to be discharged and withdrawn is a vector Exand originally long, and hence it is easy to discharge and withdraw thehigh-speed ions. Further, since the size of a vector Ez, to which thehigh-speed ions are to be deflected by applying Lorentz force, isoriginally short, Larmor radius thereof can be made short and thus aflux density necessary for the withdrawal becomes low. In contrast, asto the apparatus of the conventional art, a direction in which thehigh-speed ions are to be discharged and withdrawn is the vector Ez, andthe size thereof is small. Thus, it is difficult to discharge andwithdraw the high-speed ions. The direction in which the high-speed ionsare to be deflected in order to avoid the collision against thecollector mirror 3 is the vector Ex, and the size thereof is large.Thus, a higher flux density is required. As a result, the apparatus ofthe conventional art requires a stronger electromagnet and the cost ofthe apparatus increases. In contrast, according to the apparatus of thefirst embodiment, even with a small flux density, discharge andwithdrawal effect can be sufficiently obtained as compared with theapparatus of the conventional art, and accordingly a relatively smallelectromagnet (magnet 40) can be employed, which provides a benefit ofreducing the apparatus cost.

An embodiment obtained by modifying the apparatus according to the firstembodiment may be also possible. Modified embodiments will be describedhereafter. The description for the same component as that of the firstembodiment will be omitted, and the description for changed parts andadded parts will be given.

Second Embodiment

FIGS. 7A and 7B show configurations of an apparatus according to asecond embodiment.

In the second embodiment, a supplementary magnet 45 or a supplementarycore 46 as magnetic force production means for further converging themagnetic lines of force at the entrance 30A of the ion withdrawal unit30 to make the flux density higher is additionally provided.

FIG. 7A shows an apparatus obtained by adding the supplementary magnet45 to the apparatus of the first embodiment as described above.

The supplementary magnet 45 surrounds the entrance 30A of the ionwithdrawal unit 30 and is disposed so as to apply a magnetic field to asmall space in the vicinity of the entrance 30A. The supplementarymagnet 45 further converges the magnetic lines of force at the entrance30A of the ion withdrawal unit 30 to make the flux density higher. Thesize of the supplementary magnet 45 can be minimized even if the fluxdensity thereof is equal to or larger than that of the magnet 40.

Since the magnetic lines of force are further converged by thesupplementary magnet 45, the efficiency of withdrawal of the high-speedions by the ion withdrawal unit 30 is enhanced and the ion withdrawalunit 30 can be made smaller. Furthermore, since the magnetic lines offorce are further converged, the diameter of the ion collection hole 3 eof the collector mirror 3 can be made short and the area for collectingthe EUV light on the collector mirror 3 can be made wide.

It may be possible to employ the configuration shown in FIG. 7B toobtain the same operation and effect as the configuration shown in FIG.7A.

FIG. 7B shows an apparatus obtained by adding the supplementary core 46to the apparatus of the first embodiment.

The supplementary core 46 surrounds the entrance 30A of the ionwithdrawal unit 30 and is disposed so as to apply a magnetic field to asmall space in the vicinity of the entrance 30A. The supplementary core46 further converges the magnetic lines of force at the entrance 30A ofthe ion withdrawal unit 30 to make the flux density higher. By using thesupplementary core 46 in place of the supplementary magnet 45, theoperation and effect same as the case in which the supplementary magnet45 is used can be obtained with a configuration simpler than the case inwhich the supplementary magnet 45 is used.

Third Embodiment

FIGS. 8A and 8B are views showing configurations of an apparatusaccording to a third embodiment.

FIGS. 8A and 8B each show an apparatus obtained by modifying theposition of the magnet 40 in the first embodiment.

The magnet 40 is disposed around the periphery of the collector mirror 3in the first embodiment while the magnet 40 in the third embodiment isdisposed on the opposite side of the collector mirror 3 from the EUVlight production point A. In other words, the magnet 40 is provided soas to surround the entrance 30A of the ion withdrawal unit 30.

The magnet 40 of the apparatus shown in FIG. 8A can be smaller than thatof the apparatus of the first embodiment However, it is necessary forthe magnet 40 to have a hole 40 a that allows the laser light L to passtherethrough.

Since the magnet 40 is provided to surround the entrance 30A of the ionwithdrawal unit 30, the magnet 40 can be miniaturized while the fluxdensity same as that of the apparatus of the first embodiment ismaintained. As mentioned above, though it is necessary for the magnet 40to have the hole 40 a, the cost of the magnet can be reduced despitethat.

The apparatus shown in FIG. 8B employs the magnet 40 that is far smallerthan that shown in FIG. 8A. For example, a small permanent magnet may beused.

Specifically, the directivity of intensity distribution of thehigh-speed ions may become very strong according to a laser irradiationmethod and the type of the target 1. In other words, the directivitybecomes very strong when a solid target having a groove or hollow, suchas a wire target with a groove, a wire target with hollows, is used inplace of a droplet target as the target 1 as will be described later.The directivity of intensity distribution of the high-speed ions isoriginally strong even when a droplet target is employed. However; thedirectivity of intensity distribution of the high-speed ions becomesfurther strong when the grove or the hollow of a solid target isirradiated with the laser light L. Since the directivity of intensitydistribution of the high-speed ions becomes stronger, the convergenceaction of the magnetic lines of force necessary for obtaining the sameion withdrawal efficiency can be made weaker, accordingly. As a result,a small permanent magnet may be employed. Since the small permanentmagnet may be employed as the magnet 40, the entire apparatus shown inFIG. 8B can be further simplified and also miniaturized.

Fourth Embodiment

FIG. 9 shows a configuration of an apparatus according to the fourthembodiment.

In the fourth embodiment, voltage application means 50 for applying avoltage on the ions is additionally provided so as to correct orbits ofthe ions at the entrance 30A of the ion withdrawal unit 30 to introducethe ions to the entrance 30A.

The apparatus shown in FIG. 9 is obtained by adding the voltageapplication means 50 comprising a direct current or pulse power supply51 and an electrode 52 to the apparatus of the above first embodiment.

The electrode 52 is provided in the vicinity of the entrance 30A of theion withdrawal unit 30. The electrode 52 is electrically connected withthe direct current or pulse power supply 51.

In the apparatus of the first embodiment, according to the shape of themagnetic lines of force, the magnetic lines of force may diverge in thevicinity of the entrance 30A.

In this view, a direct current voltage or pulsed voltage is applied onthe electrode 52 by the direct current or pulse power supply 51. Whenthe applied voltage is direct current, it is preferable to make thepolarity of the electrode coincide with that of the ions. Accordingly,the orbits of the ions, which are charged particles, are corrected by arepulsion of the electric field, whereby the ions are introduced intothe entrance 30A of the ion withdrawal unit 30.

When the applied voltage is a pulsed voltage, the polarity may bechanged according to the timing of applying the voltage on the electrode52. Specifically, a voltage having a polarity opposite to that of theions is applied at the timing when the ions pass through a region wherethe magnetic lines of force tend to diverge, while a voltage having thesame polarity as that of the ions is applied at the timing when the ionspass in the vicinity of the entrance 30A of the ion withdrawal unit 30.As a result, the orbits of the ions, which are charged particles, arecorrected and thus the ions are introduced into the entrance 30A of theion withdrawal unit 30.

As described above, according to this embodiment, the orbits of thehigh-speed ions converged by the magnetic field are corrected by theelectric field, and accordingly the high-speed ions are introduced intothe entrance 30A of the ion withdrawal unit 30. Consequently, theefficiency of withdrawal of the ions by the ion withdrawal unit 30 isenhanced.

Fifth Embodiment

FIGS. 10A through 10C show configurations of an apparatus according tothe fifth embodiment.

In the fifth embodiment, magnetic line of force production means 47, 48,and 49 for producing magnetic lines of force is provided in order todeflect the ions toward the entrance 30A of the ion withdrawal unit 30.In addition, the laser condenser system 8 and the magnet 40 are disposedsuch that the incident axis of the laser light L and the central axis ofthe magnetic field coincide or approximately coincide.

The apparatus shown in FIG. 10A is obtained by adding the magnet 47 fordeflection to the apparatus of the above first embodiment.

In the first embodiment, the laser light axis is inclined at apredetermined angle with respect to the collector mirror center axis 3c. However, according to the fifth embodiment, the driver laser unit 4and the laser condenser system 8 are disposed such that the laser lightincidence axis and the collector mirror central axis 3 c coincide orapproximately coincide. On the other hands, the magnet 40 is disposedsuch that the magnetic field central axis and the collector mirrorcentral axis 3 c coincide or approximately coincide. Accordingly, theincident axis of the laser light L and the central axis of the magneticfield coincide or approximately coincide. The magnet 47 for deflectionis provided for deflecting the high-speed ions to be withdrawn in orderto avoid a collision of the high-speed ions against the laser condensersystem 8. Correspondingly, the ion withdrawal unit 30 is disposed alsoto be inclined with respect to the laser light incidence axis.

The magnet 47 for deflection is provided on the opposite side of thecollector mirror 3 from the EUV light production point A. The magnet 47for deflection is also provided between the collector mirror 3 and theion withdrawal unit 30. The central axis of the magnet 47 for deflectionis shifted with respect to the central axis 3 c of the collector mirror3.

The magnet 47 is smaller than the main magnet 40, and is disposed so asto surround the laser light axis.

After passing through the collector mirror 3, the high-speed ions aredeflected by the small magnet 47 for deflection, and are introduced intothe entrance 30A of the ion withdrawal unit 30.

According to this embodiment, since the incident axis of the laser lightand the collection axis (mirror central axis 3 c) of the collectormirror 3 coincide or approximately coincide, alignment operation becomeseasy. The ions are deflected after having passed through the collectormirror 3, and advance on or approximately on the laser light incidenceaxis at the time of passing through the collector mirror 3. Thus, theion collection hole 3 e and the laser passage hole 3 d of the collectormirror 3 may be one and the same. As a result, an area (area of thereflective plane) for collecting light on the collector mirror 3 can beincreased.

The apparatus shown in FIG. 10B comprises a core 48 for deflection inplace of the magnet 47 for deflection of the apparatus shown in FIG.10A. The arrangement of the core 48 is the same as that of the magnet 47of the apparatus shown in FIG. 10A, and the operation and effect same asthe apparatus shown in FIG. 10A can be obtained. Further, since the coreis used in place of a magnet, the effect of simple structure and lowcost can be obtained.

The apparatus shown in FIG. 10C comprises the small magnet 49 similar tothe magnet 47 shown in FIG. 10A. It is, however, to be noted that themagnet 49 is disposed to deviate off the laser light axis. With theapparatus shown in FIG. 10C, the same operation and effect as theapparatus shown in FIG. 10A can be achieved. In addition, the laserlight path is apart from the magnetic field, which brings about aneffect that a small number of the high-speed ions leaked from themagnetic field can also be prevented from colliding against the lasercondenser system 8.

Sixth Embodiment

FIGS. 11A through 11C show configurations of an apparatus according tothe sixth embodiment.

In the sixth embodiment, voltage application means 55 for applying avoltage on the ions is provided so as to deflect the ions toward theentrance 30A of the ion withdrawal unit 30. Also, like the fifthembodiment above, the laser condenser system 8 and the magnet 40 aredisposed such that the incident axis of the laser light L and thecentral axis of the magnetic field coincide or approximately coincide.

The apparatus shown in FIGS. 11A through 11C is obtained by adding thevoltage application means 55 for deflection to the apparatus of theabove first embodiment.

In detail, the apparatus shown in FIGS. 11A through 11C is obtained byadding the voltage application means 55 comprising a direct current orpulse power supply 56 and an electrode 57 to the apparatus of the abovefirst embodiment.

Like the fifth embodiment described above, the ion withdrawal unit 30 isdisposed to be inclined with respect to the laser light incidence axis.

The electrode 57 is provided between the collector mirror 3 and the ionwithdrawal unit 30. The electrode 57 is electrically connected with thedirect current or pulse power supply 56.

In the apparatus shown in FIG. 11A, the direct current or pulse powersupply 56 applies a voltage having a polarity opposite to that of theions on the electrode 57. When the ions are charged particles having aplus polarity, a voltage having a minus polarity is applied. Afterpassing through the collector mirror 3, the high-speed ions aredeflected to be attracted toward the electrode 57 due to an electricfield caused by the electrode 57 and then introduced into the entrance30A of the ion withdrawal unit 30.

According to this embodiment, since the incident axis of the laser lightand the collection axis (mirror central axis) of the collector mirror 3coincide or approximately coincide, alignment operation becomes easy.Additionally, the ions are deflected after having passed through thecollector mirror 3, and advance on or approximately on the laser lightincidence axis at the time of passing through the collector mirror 3.Thus, the ion collection hole 3 e and the laser passage hole 3 d of thecollector mirror 3 may be one and the same. Since the shape of theelectrode 57 is adaptable as compared with that of a magnet, it ispossible to increase the design flexibility and decrease the number ofparts.

In the apparatus shown in FIG. 11B, the direct current or pulse powersupply 56 applies a voltage having the same polarity as that of the ionson the electrode 57. When the ions are charged particles having a pluspolarity, a voltage having a plus polarity is applied. After passingthrough the collector mirror 3, the high-speed ions are deflected todepart from the electrode 57 due to an electric field caused by theelectrode 57 and then introduced into the entrance 30A of the ionwithdrawal unit 30. According to this embodiment, the same effect as theapparatus shown in FIG. 11A can be obtained.

In the apparatus shown in FIG. 11C, the electrode 57 shown in FIG. 11Aand the electrode 57 shown in FIG. 11B are provided, and the voltagehaving the polarity opposite to that of the ions like the apparatusshown in FIG. 11A and the voltage having the same polarity as that ofthe ions like the apparatus shown in FIG. 11B are respectively applied.

The direct current or pulse power supplies 56 and 56 apply a voltagehaving a polarity opposite to that of the ions and a voltage having thesame polarity as that thereof on the electrodes 57 and 57, respectively.After passing through the collector mirror 3, the high-speed ions aredeflected to be attracted toward one electrode 57 and to depart from theother electrode 57 due to an electric field caused by the electrodes 57and 57, and then introduced into the entrance 30A of the ion withdrawalunit 30. According to this embodiment, the same effect as the apparatusshown in FIGS. 11A and 11B can be obtained.

Either a direct current voltage or a pulsed voltage may be available asa voltage applied on the electrode 57 by the direct current or pulsepower supply 56. In detail, however, when the pulsed voltage is applied,there is an advantage that the collision of the ions against theelectrode 57 can be prevented though the cost of the direct current orpulse power supply 56 is high, compared with the case where the directcurrent voltage is applied.

Seventh Embodiment

FIG. 12 shows a configuration of an apparatus according to the seventhembodiment.

The seventh embodiment is made by combining the fifth and sixthembodiments.

In the seventh embodiment, like the fifth embodiment, magnetic lineproduction means 47 for producing magnetic lines of force is provided soas to deflect the ions toward the entrance 30A of the ion withdrawalunit 30. For example, the magnet 47 for deflection is provided like theapparatus shown in FIG. 10A.

Also, the voltage application means 55 for applying a voltage on theions is provided so as to deflect the ions toward the entrance 30A ofthe ion withdrawal unit 30 as is the case with the sixth embodiment. Forexample, the direct current or pulse power supply 56 applies a voltagehaving the same polarity as that of the ions on the electrode 57 likethe apparatus shown in FIG. 11B.

Further, like the fifth and sixth embodiments, the laser condensersystem 8 and the magnet 40 are disposed such that the incident axis ofthe laser light L and the central axis of the magnetic field coincide orapproximately coincide.

According to the seventh embodiment, after passing through the collectormirror 3, the high-speed ions are deflected so as to depart from theelectrode 57 due to an electric field caused by the electrode 57. Theions are further deflected by the small magnet 47 for deflection andintroduced into the entrance 30A of the ion withdrawal unit 30.

According to this embodiment, the same effects as the fifth and sixthembodiments can be obtained. In addition, since the high-speed ions arefar strongly deflected, the damage caused by the collision of thehigh-speed ions against the laser condenser system 8 can be reduced.

Eighth Embodiment

FIG. 13 shows a configuration of an apparatus according to the eighthembodiment.

The ions are made deflected by a magnetic field and/or an electric fieldin the fifth, sixth, and seventh embodiments described above. Themagnetic lines of force may be deflected toward the entrance 30A of theion withdrawal unit 30 by disposing the magnet 40 itself of theapparatus in the first embodiment to be inclined with respect to thecollector mirror 3.

Specifically, as shown in FIG. 13, the magnet 40 is disposed so as to beinclined with respect to the collector mirror 3. It should be noted,however, that, in terms of a relationship with the laser condensersystem 8, the magnet 40 is disposed such that the incident axis of thelaser light L and the central axis of the magnetic field coincide orapproximately coincide.

According to the eighth embodiment, the magnetic lines of force aredeflected toward the entrance 30A of the ion withdrawal unit 30. Hence,after passing through the collector mirror 3, the high-speed ions areintroduced into the entrance 30A of the ion withdrawal unit 30 along thedeflected magnetic lines of force. Further, according to the eighthembodiment, there is an advantage that the configuration thereof can besimplified significantly though the collision of the ions against thelaser condenser system 8 sometimes occurs.

Ninth Embodiment

FIG. 14 shows a configuration of an apparatus according to the ninthembodiment.

In this embodiment, a collector mirror 8A is used as the laser condensersystem 8. Further, when copper or the like is employed as the base metalof the collector mirror 8A, the collector mirror 8A acts as a deflectionelectrode having the same function as the electrode 57 of the sixth andseventh embodiments described above.

Specifically, in the ninth embodiment, voltage application means 58 forapplying a voltage on the ions is provided so as to deflect the ionstoward the entrance 30A of the ion withdrawal unit 30. Moreover, likethe fifth, the sixth, the seventh, and the eighth embodiments describedabove, the laser condenser system 8 and the magnet 40 are disposed suchthat the incident axis of the laser light L and the central axis of themagnetic field coincide or approximately coincide.

The voltage application means 58 includes a direct current or pulsepower supply 56 and the collector mirror 8A that functions as anelectrode. The collector miller 8A is a constituent of the lasercondenser system 8.

The ion withdrawal unit 30 is disposed so as to be inclined with respectto the laser light incidence axis, like the apparatus of the fifth,sixth, seventh, and eighth embodiments described above.

The collector mirror 8A is provided between the collector mirror 3 andthe ion withdrawal unit 30. The collector minor 8A is electricallyconnected with the direct current or pulse power supply 56.

In the apparatus shown in FIG. 14, the direct current or pulse powersupply 56 applies a voltage having the same polarity as the ions on thecollector mirror 8A. When the ions are charged particles having a pluspolarity, a voltage having a plus polarity is applied. After passingthrough the collector mirror 3, the highspeed ions is deflected so as todepart from the collector mirror 8A due to an electric field caused bythe collector mirror 8A and then introduced into the entrance 30A of theion withdrawal unit 30.

According to the ninth embodiment, since the high-speed ions aredeflected so as to depart from the collector mirror 8A, the collision ofthe ions against the collector mirror 8A can be suppressed. Further,since the laser light incidence axis, the central axis of the magneticfield, and the central axis 3 c of the collector mirror 3 coincide, itis easy to adjust the alignment thereof with a simple configuration.

Tenth Embodiment

In each embodiment described above, the descriptions have been given onthe assumption that a droplet target is employed as the target 1.

However, it may be possible to employ targets other than the droplet 1Aas the target 1.

FIG. 15A shows a case in which a rotating disk target 1B is employed asthe target 1. The rotating disk target 1B is made by lamination in whicha target material such as tin Sn is coated on a surface 1 e of arotating disk.

EUV light is produced by emitting the laser light L on the rotatingsurface 1 e of the rotating disk target 1B while the rotating disktarget 1B is being rotated.

When the rotating disk target 1B is irradiated with the laser light L,the directivity of intensity distribution of the high-speed ions becomesstrong as compared with a case where the droplet 1A is irradiated.Consequently, this makes the convergence of the high-speed ions easy,further enhancing the efficiency of collection and withdrawal.

FIG. 15B shows a case in which a grooved wire target 1C is employed asthe target 1. The grooved wire target 1C is formed by a wire having agroove 1 f in the longitudinal direction, and is made by lamination inwhich a target material such as tin Sn is coated on at least the groove1 f of the wire.

The EUV light is produced by emitting the laser light L on the groove 1f while the grooved wire target 1C is being moved in the longitudinaldirection.

When the grooved wire target 1C is irradiated with the laser light L,the directivity of intensity distribution of the high-speed ions becomesfar strong as compared with a case where the rotating disk target 1B isirradiated. Moreover the efficiency of conversion from laser energy toEUV light energy can be further enhanced. Additionally, the same effectcan be also obtained by using a rotating disk having a groove thereon asthe target 1.

FIG. 15C shows a case in which a hollowed wire target 1D is employed asthe target 1. The hollowed wire target 1D is formed by a wire havinghollows 1 g formed at intervals in the longitudinal direction, and ismade by lamination in which a target material such as tin Sn is coatedon at least the hollows 1 g of the wire.

When the hollowed wire target 1D is irradiated with the laser light L,the directivity of intensity distribution of the high-speed ions becomesfar strong as compared with a case where the grooved wire target 1C isirradiated. Moreover, the efficiency of conversion from laser energy toEUV light energy can be further enhanced.

What is claimed is:
 1. An ion withdrawal apparatus that withdraws ionsemitted from a plasma in an EUV light production apparatus in which atarget at an EUV light production point is irradiated with laser lightto make a plasma state and the target emits EUV light, the ionwithdrawal apparatus comprising: a collector mirror that is disposed ina direction opposite to a laser light incidence direction to collect theEUV light and has an ion-collecting hole for the ions to passtherethrough; first magnetic line of force production means thatproduces a magnetic line of force that is parallel or approximatelyparallel to the laser light incidence direction at or in the vicinity ofthe EUV light production point; and ion withdrawal means that isdisposed on the opposite side of the EUV light production point acrossthe ion-collecting hole of the collector mirror and on the side facingthe EUV light production point, and withdraws the ions, an entrance ofthe ion withdrawal means being open to the ion-collecting hole.
 2. Theion withdrawal apparatus according to claim 1, wherein the collectormirror has a laser-passing hole for the laser light to pass therethroughand reach the EUV light production point.
 3. The ion withdrawalapparatus according to claim 2, comprising voltage application meansthat applies a voltage on the ions so as to deflect the ions toward theentrance of the ion withdrawal means.
 4. The ion withdrawal apparatusaccording to claim 1, wherein the laser light incidence direction is ata predetermined angle with respect to a central axis of the collectormirror and the entrance of the ion withdrawal means is disposed on thecentral axis of the collector mirror.
 5. The ion withdrawal apparatusaccording to claim 1, wherein an incident axis of the laser light and acentral axis of the collector mirror coincide or approximately coincideand an entrance of the ion withdrawal means is disposed to deviate offthe central axis of the collector mirror.
 6. The ion withdraw apparatusaccording to claim 1, further comprising second magnetic line of forceproduction means that further converges, the magnetic line of force atthe entrance of the ion withdrawal means to make a flux density higher.7. The ion withdrawal apparatus according to claim 1, wherein the firstmagnetic line of force production means is disposed on the opposite sideof the EUV light production point across the ion-collecting hole of thecollector mirror and on the side facing the EUV light production point.8. The ion withdrawal apparatus according to claim 1, comprising voltageapplication means that applies a voltage on the ions to correct orbitsof the ions at the entrance of the ion withdrawal means to introduce theions into the entrance.
 9. The ion withdrawal apparatus according toclaim 1, further comprising second magnetic line of force productionmeans that produces the magnetic line of force so as to deflect the ionstoward the entrance of the ion withdrawal means.
 10. The ion withdrawalapparatus according to claim 1, wherein the magnetic line of force isdeflected toward the entrance of the ion withdrawal means by disposingthe first magnetic line of force production means so as to be inclinedwith respect to the collector mirror.
 11. The ion withdrawal apparatusaccording to claim 1, wherein the target is a rotating disk target, agrooved wire target or a hollowed wire target.